Analog Devices UG-065 User Manual

Evaluation Board User Guide

One Technology Way • P.O. Box 9106 • Norwood, MA 02062-9106, U.S.A. • Tel: [phone] • Fax: [phone] • www.analog.com

UG-065

iMEMS ADXL345 Inertial Sensor Datalogger and Development Board

FEATURES

Ultralow power ADXL345 accelerometer
Inertial sensor development board
Datalogs onto MicroSD card
Fully programmable via serial interface; firmware examples

provided

Battery-powered for portable applications

REQUIREMENTS

2 AAA batteries
MicroSD card and card reader (for datalogging)
Computer with serial port (for programming)

Figure 1. Inertial Sensor Development Board

08658-001

GENERAL DESCRIPTION

It is often a time saver in hardware development to make progress
on the firmware and the hardware simultaneously. The challenge is
that it proves difficult to develop firmware before the hardware
exists. The iMEMS® ADXL345 development board is an easy­to-use tool that facilitates prototyping by providing a platform
that can be duplicated in the final application. Additionally, the
development board can be configured as a datalogger and can
be used to gather data for refining algorithms, tuning thresholds,
and generally familiarizing oneself with accelerometer data.

Two AAA batteries power the development board and thus it
integrates seamlessly into portable applications. Communications
and processing is done by an ARM7-based ADuC7024 micro­controller, and the interface provided is fully reprogrammable.
Moreover, all ADuC7024 pins are broken out into headers to
facilitate design of compatible expansion boards. Data is logged
onto a MicroSD memory card, providing essentially unlimited
memory capacity and operating system versatility. Data is stored in
a text file; therefore, there is no need to install any software to
operate the board or read data. Software is provided to assist
with programming the board.

Please see the last page for an importan t warning and disclai mers.

Rev. 0 | Page 1 of 8

UG-065 Evaluation Board User Guide

TABLE OF CONTENTS

Features.............................................................................................. 1

Requirements .................................................................................... 1

General Description ......................................................................... 1

Revision History ............................................................................... 2

Overview............................................................................................ 3

Features.......................................................................................... 3

Using the Board ................................................................................ 4

REVISION HISTORY

2/10—Revision 0: Initial Revision

Getting Started...............................................................................4

Programming the Board...............................................................4

Software Tools................................................................................4

Board Layout and Schematics..........................................................6

ESD Caution...................................................................................8

Rev. 0 | Page 2 of 8

Evaluation Board User Guide UG-065

(A) RESET

AND PROG RELEASED

(B) PUSH PROG

(C) PUSH RESET

OVERVIEW

The ADXL345 inertial sensor development board has the
following features:

• A 2-layer printed circuit board (PCB), 1.125-inches × 2.25­inches form factor

• A two AAA battery power supply

• A 4-pin UART header to connect to RS232 interface cable

• Reset/download push-buttons

• Power indicator/general-purpose LEDs

• Access to all microcontroller I/Os from the external
header; all device pins are brought out to the external
header pins

• Demonstration firmware

FEATURES

Power Supply

A pair of AAA batteries powers the board, and the battery
holder is located on the back of the board. An on/off switch on
the lower left of the front of the board controls power to it. The
battery voltage is not regulated but is decoupled with a 10 µF
capacitor globally, and an additional 1 µF capacitor at the device
supply pins to ground.

RS232 Interface

The ADuC7024 (UC1) P1.1 and P1.0 lines are connected to the
RS232 interface cable via the connector (UART). The interface
cable generates the required level shifting to allow direct
connection to a PC serial port. Ensure that the supplied cable
is connected to the board correctly, that is, VDD is connected to
VDD and GND is connected to GND.

RESET/PROG Push-Buttons

A RESET push-button is provided to allow the user to manually
reset the part. When inserted, the RESET pin of the ADuC7024
is pulled to GND. Because the RESET pin on the ADuC7024 is
Schmitt-triggered internally, there is no need to use an external
Schmitt trigger on this pin.

To enter serial download mode, the user must hold the P0.0/BM
pin low while reset is toggled. On the development board, serial
download mode can be easily initiated by holding down the
serial download push-button (PROG) while inserting and
releasing the reset button (RESET), as illustrated in Figure 2.

Power Indicator/General-Purpose LEDs

Two general-purpose LEDs are available on the board. A red
LED (LED1) is connected to P4.5 of the ADuC7024, and a
green LED (LED2) is connected to P4.4. Both LEDs can be
repurposed via firmware.

Breakout Header

All ADuC7024 pins are brought out to headers on either side of
the board. The headers come unpopulated but can be populated
using standard 0.1-inch header pins.

The thin form factor of the top of the board allows the design of
an expansion board to connect above the development board,
with the header pins providing both electrical and physical
connections.

Firmware

Sample firmware is provided on the ADXL345 product page.

RESET PROG

RESET PROG

Figure 2. Entering Serial Download Mode to Reprogram the Board

(D) RELEASE RESET

RESET PROG

RESET PROG

Rev. 0 | Page 3 of 8

(E) RELEASE PROG

RESET

PROG